Sheet metal stamping and spot welding are the traditional technologies used to form interior and exterior panels for vehicles and other durable goods. Sheet metal stamping processes for making automotive panels include blanking, drawing, trimming and flanging. In addition to this traditional sequence of stamping operations, a restrike operation or secondary trimming operation may be involved. This method of manufacturing was employed to make parts from mild steel for decades.
New fuel economy standards require car designers to use lighter and stronger materials such as Advanced High Strength Steels (“AHSS”)/Ultra High Strength Steels (“UHSS”) and Aluminum alloys. AHSS/UHSS save weight by reducing the material thickness that is compensated for by the increased strength of the replacement materials. However, design and gauge selection of many interior panels and structural parts are driven by bending and torsion stiffness.
Simple replacement of mild steels with thinner higher strength steels degrades the elastic bending and torsion performance characteristics of parts made by the higher strength materials. These performance characteristics of high strength materials are the major roadblocks that limit implementation of AHSS and UHSS in the automotive industry. Insufficient bending stiffness of stamped panels made of AHSS and UHSS steels also works against broad adoption of these materials in other durable goods.
One proposed solution that is currently being implemented is patching portions of the parts with over laid patches in local areas where the stamped blank has insufficient stiffness. For example, a hot stamped patch of Boron steel may be applied to a portion of a B-pillar reinforcement. In another example, a patch of high strength material may be bonded by polyurethane to a portion of a roof panel for reinforcing the roof. Providing a patch of the high strength materials adds weight to the vehicle and reduces the advantages offered by the adoption of high strength materials.
The problem of insufficient stiffness of stamped panels that have a design driven by elastic bending requirements and torsional stiffness is addressed by this disclosure. The lack of elastic stiffness results in the use of blanks that have an increased gauge that is counterproductive to weight savings.
The above problems and other problems are addressed by this disclosure as summarized below.